The type of wire guide disclosed here is designed to be used in connection with a rotary wire stripper of the kind disclosed in U.S. Pat. No. 4,745,828 (the '828 stripper), although it is also applicable to other rotary stripper configurations. The '828 stripper has a pair of diametrically opposed blades driven in rotation so that their cutting edges circle about the end of a wire that is to be stripped. As the blades circle, they are simultaneously moved in a symmetrical fashion radially inwardly until their cutting edges contact and out the wire's insulation to a predetermined depth. The cut insulation at the end of the wire, which is commonly called a "slug", is then stripped from the wire by pulling it axially outwardly.
FIGS. 10 and 11, both of which are labeled "prior art", provide an exaggerated view of certain "U" shaped wire guides that, prior to the present invention, have commonly been used in conjunction with the '828 stripper for centering the wire to be stripped relative to the stripper's blades. Referring first to Fig. 10, the '828 patent calls its "U" shaped wire guides "centering jaws" which are indicated at 1, 3. As just mentioned, these function to center a wire 5 as the slug 7 covering the center conductor 9 at its end is stripped.
The centering jaws 1, 3 and stripper blades 11, 13 both rotate about the wire 5 is the blades are moved inward to cut the insulation. As is clearly evident from the description in the '828 patent, the blades 11, 13 slidingly move within the "U" of the centering jaws 1, 3 at least partially independently of the radial inward movement of the jaws. In other words, both the jaws 1, 3 and blades 11, 13 generally move simultaneously inwardly toward the wire 5 until the jaws 1, 3 first contact the outer surface of the wire's insulation. This is indicated at 15 and 17 in Fig. 10.
Further radial inward movement by the jaws 1, 3 is, at that point, prevented by the wire's insulation as it resists the force provided by a central spring that moves the jaws (see reference numeral -8 in Fig. 1 of the '828 patent). However, the blades 11, 13 are separately driven inward, as is schematically indicated by dashed lines 19 and 21, and continue to cut inwardly, sliding, along jaws 1, 3, until they substantially cut through the insulation. Thereafter, both the jaws 1, 3 and blades 11, 13 are pulled axially away from the wire's end in the manner schematically indicated at 23 and 25 in FIG. 11.
The stripper's blades 11, 13 continue to rotate and remain near the wire's center conductor 9 as they are pulled away. Their beveled edges 27, 29 are what engage with and actually pull the slug 7 off the wire's end. The wire itself is constrained from moving by nonrotating clamping jaws 31, 33 which hold the wire 5 inwardly of slug 7. For further reference, these clamping jaws 31, 33, which are different from centering jaws 1, 3, are indicated by reference numeral 11 in the '828 patent.
As soon as the centering jaws 1, 3 clear the wire's insulation beyond the blade-cut position, which is shown at 35, 37 in FIG. 11, there is nothing to otherwise center the wire's end relative to the blades. What this means is that the slug is essentially free to jiggle back and forth in the directions indicated by arrow 39. This will bring center conductor 9 into contact with the rotating blades -1, 13 and create nicks.
Generally, the '828 stripper is intended for use on a special subcategory wire type (co-axial wire) which typically is constructed of very soft, thick insulation. This allows stoppage of blade closure significantly before encounter of the conductor, thus avoiding nicking the conductor. The '828 stripper was not designed to strip thin insulation and cannot do so without nicking the conductor.
Minor nicking is not a problem in many or most manufacturing environments. However, airplane, government and military requirements dictate that no nicks can be present in wires used on many aircraft. Therefore, although the '828 stripper is excellent for use in stripping wires where nicking does not impose a constraint on manufacturing, it has not, prior to the implementation of the present invention and the related copending applications cited above, been useful for stripping wires having hard, thin insulation which is typical for aircraft use. This problem has led to the development of the wire guide structure disclosed here.
A significant difference between the '828 centering jaws 1, 3 shown in FIGS. 10 and 11, and a pair of wire guides constructed in accordance with the present invention, is that the jaws 1, 3 grip the wire 5 on those sides 11a, 13a of the stripper's blades which are opposite from the sides 11b, 13b facing the slug 7. That is to say, the guides of the present invention grip the slug itself. This difference, and its advantages, will become apparent upon consideration of the following description.